The present invention relates to a fan guard, and more particularly, a fan guard for a ventilation unit that is mounted on an air port of a ventilation unit that has a ventilation fan.
A fan guard is provided in an air port of a ventilation fan in a ventilation unit in, for example, an outdoor unit of an air conditioner. The fan guard is a member for protecting the ventilation fan.
Conventional fan guards that are made from plastic and integrally formed into a plurality of radially disposed radiating ribs and a plurality of concentrically disposed annular ribs are well known. These types of plastic fan guards have a long, slender and flat shape along the axial direction of the ventilation fan in order to maintain strength and reduce pressure loss.
In the aforementioned conventional fan guard, when a propeller fan is used as a ventilation fan, the radiating ribs and the annular ribs easily create a problem in which they interfere with flow of air from the ventilation fan into the fan guard In other words, the air flow from the propeller fan is a swirling divergent flow that has a velocity component of a predetermined size in the rotational and axial directions of the propeller fan. With regard to this type of swirling divergent flow, because the radiating ribs and the annular ribs are flat along the axial direction of the ventilation fan, there is a fear that the radiating ribs and the annular ribs will collide with the air flow and generate vortices, and that this will give rise to pressure loss and the generation of noise.
In addition, because the wide space between the outer circumferential portions of the radiating ribs and the flat members of the annular ribs along the axial direction, problems exist in which the rigidity of the outer circumferential portions weaken and the rigidity of the fan guard in the thickness direction is easily lowered. When the rigidity in the thickness direction is lowered, there is a particular fear that the fan guard in a top-blowing outdoor unit will come into contact with the ventilation fan in the wintertime when snow accumulates on the fan guard and warps it.
An object of the present invention is to make a fan guard of a ventilation unit that can suppress pressure loss and noise, and maintain a high level of rigidity in the thickness direction.
A fan guard of a ventilation unit according to the first aspect of the present invention is mounted on an air discharge port of a ventilation unit having a ventilation fan, and is comprised of an outer frame, a plurality of first ribs, and a plurality of second ribs. The outer frame is disposed around the outer perimeter of the air discharge port. The plurality of first ribs extend radially outward from the vicinity of the center of the outer frame and are curved in the rotational direction of the ventilation fan. The plurality of second ribs are integral with the first ribs, and with the rotational axis of the ventilation fan as the center, are disposed in concentric rings that are spaced apart at a predetermined distance in the radial direction and at least those in the outer circumference are formed such that they follow the flow of blown air from the ventilation fan and are slanted toward the outer radial direction.
In the fan guard of ventilation unit, when the ventilation fan rotates and generates a flow of rotating divergent blown air in the rotational direction and the axial direction having a velocity component of a predetermined size, the flow of the blown air passes through the first ribs and the second ribs. At this time, because the first ribs are curved in the rotational direction, by curving them such that they follow the rotating divergent current of the blown air, it is difficult for the blown air to collide with first ribs, and it is to eliminate resistance to the blown air. In addition, the second ribs are slanted outward in the radial direction such that they follow the flow of blown air, and thus it is difficult for the flow of blown air to collide with the second ribs, and there is little resistance to the flow of blown air by the second ribs. Because of this, even if first and second ribs are provided, the flow of blown air is smooth, and pressure drop and noise can be suppressed. Moreover, because the second ribs are slanted to follow the flow of blown air, the width of the second ribs (the length of the thickness of second ribs in the direction that they intersect) are longer than when they are not slanted, and the resilience of the fan guard in the thickness direction can be maintained at a high level.
With the fan guard of the ventilation unit according to the second aspect of the present invention, the first ribs of the guard in the disclosure of the first aspect are formed such that they are slanted toward the downstream side of the rotational direction to follow the flow of air blown from the ventilation fan. In this situation, both the first and second ribs are slanted to follow the flow of the blown air, and thus the resistance to the flow of blown air can be further reduced and pressure drop and noise can be further suppressed.
With the fan guard of the ventilation unit according to the third aspect of the preset invention, the slanting angles of the first ribs and the second ribs of the guard disclosed in the second aspect are different, and built up portions are formed at the points where the first ribs and the second ribs intersect. In this situation, even when both first and second ribs are slanted outward and undercut portions are produced, the undercut portions can be eliminated with the built up portions. Because of this, it is easy to remove the fan guard from a mold, and is easy to integrally form the fan guard from plastic or the like. Moreover, because the cross sectional area of the fixed portion that enlarges the highest bending moment in the second ribs is large, the second ribs are even more resilient, and the resilience of the fan guard in the thickness direction can be maintained at an even higher level.
With the fan guard of the ventilation unit according to the fourth aspect of the present invention, the first ribs of the guard in the disclosure of the second or third aspect are formed such that they are slanted toward the downstream side of the rotational direction 20 to 40 degrees with respect to a first reference plane that is parallel to the rotational axis of the ventilation fan. In this situation, the slant of the first ribs are ideal with respect to the flow of the rotating blown air.
With the fan guard of the ventilation unit according to the fifth aspect of the present invention, the second ribs of the guard in the disclosure of the fourth aspect are formed such that they are slanted outward 5 to 15 degrees with respect to a cylindrical second reference plane that is concentric with the rotational axis of the ventilation fan. In this situation, the slant of the second ribs are ideal with respect to the spread of the rotating blown air.
The fan guard of the ventilation unit according to the sixth aspect of the present invention is a guard disclosed in any of the first through fifth aspects, and further comprises a closing plate, the closing plate facing a hub of a ventilation fan that is a propeller fan having a cylindrical hub positioned in the center thereof and a plurality of blades provided around the circumference of the hub and disposed in the same center as that of the rotational axis of the ventilation fan, and wherein the first ribs are formed such that they extend from the closing plate to the outer frame. In this situation, because the closing plate covers the portion of the hub in the ventilation fan that does not contribute to ventilation, it is easy to prevent a reverse flow of the ventilation fan.
With the fan guard of the ventilation unit according to the seventh aspect of the present invention, the closing plate of the guard disclosed in the sixth aspect has a circular shape that is larger than the diameter of the hub. In this situation, because the bases of the blades of the ventilation fan are also covered by the closing plate when a reverse flow is easily generated, it will be more difficult to generate a reverse flow.
With the fan guard of the ventilation unit according to the eighth aspect, the first ribs of the guard disclosed in any of the first through seventh aspects are formed in a trochoidal curve. In this situation, the curve of the first ribs will easily follow the flow of the blown air.
With the fan guard of the ventilation unit according to the ninth aspect of the present invention, only the second ribs on the outer circumference of the guard disclosed in any of the sixth through eighth aspects are slanted, and the second ribs in the inner circumference are not slanted. In this situation, because, from amongst the plurality of second ribs, the only slanted ribs are in the outer circumference where the velocity of the flow of blown air is fast and the flow easily extends outward, the mold for an integrally formed fan guard is easily manufactured.
With the fan guard of the ventilation unit according to the tenth aspect of the present invention, the second ribs in the guard disclosed in the ninth aspect that are slanted are those in the outer circumference beyond ⅓ of the length of blades in the radial direction of the ventilation fan. In this situation, because, from amongst the plurality of second ribs, the only slanted ribs are those in the outer circumference beyond ⅓ of the length of blades of the ventilation fan where the velocity of the flow of blown air is fast and the flow easily extends outward, the mold for an integrally formed fan guard is easily manufactured.
With the fan guard of the ventilation unit according to the eleventh aspect of the present invention, the second ribs in the guard disclosed in the ninth aspect that are slanted are those in the outer circumference beyond xc2xd of the outer diameter of the outer frame. In this situation, because, from amongst the plurality of second ribs, the only slanted ribs are those in the outer circumference beyond xc2xd of the outer diameter of the outer frame where the velocity of the flow of blown air is fast and the flow easily extends outward, the mold for an integrally formed fan guard is easily manufactured.